Climate and Discharge Trends, and Flood Hazard in Slovenia’s Dinaric Karst Region Since the Mid-Twentieth Century

The temperature, precipitation, and snow-cover data collected at the meteorological stations in the Slovenia’s Dinaric Karst region between 1961 and 2020 indicate rapid and clear climate change. During this period, temperatures increased by 2.5 °C on average, precipitation decreased by 50–400 mm on average, and the number of days with snow cover declined by 30–60%. Several studies have confirmed that these changes have a strong impact on water conditions. What is alarming is especially a decrease in the average minimum and mean discharges, and a downward trend can also be observed for many average maximum discharges. Over the past sixty years, the climate in Slovenia’s Dinaric Karst region has become warmer and drier, and there has been a significant reduction in the volume of water at most gauging stations in the area studied. Based on the trends described, a significantly smaller flood hazard would be expected, but data from the past decades suggest the opposite. The following are highlighted as possible reasons for the current flood hazard: upward trends in absolute maximum discharges in individual river basins, a slightly downward trend in absolute maximum discharges and their simultaneously greater variability, various forms of land development that used to be avoided due to the risk of flooding, and more frequent short-term extreme precipitation events causing flash floods on smaller streams.